Logic problem parking lot simulation

I'm writing a matlab code based on this problem where I already get an array of hours and I need to find the total cost. I'm not sure if I'm doing it right based on my planning.

First 30 minutes $2.50 and each additional 15 minutes or fraction thereof is $ 1.00.

Would I assume that I'd be charged 2.50 no matter how long I parked for, given that in the first few minutes when I parked it is under 30 minutes or exactly 30 minutes?

What does "fraction thereof" mean? If I parked for like 35 mins would the total cost be 3.50 then?

[Torsten]

Yes. For each time greater than 30 minutes and less or equal 45 minutes, you pay $3.50.

Best wishes

Torsten.